Coordination between the root endodermis and endosymbioses. – ENDOSYMB

Plant roots are vital for survival and growth as they regulate the intake of water and nutrients from the soil along with their transport to the shoot. Roots develop specific diffusional barriers in the endodermis, a cell layer separating the inner parts from the external parts of the root. These barriers balance uptake of nutrients, water, and interactions with soil microorganisms. Roots are also able to form symbioses with beneficial microbes such as arbuscular mycorrhizal fungi or nitrogen-fixing rhizobial bacteria to assist in nutrient acquisition. These symbioses form specific structures in the outer parts of the roots where reciprocal exchange of nutrients occurs. However, it is still unclear how the transfer of nutrients occurs between these symbiotic structures and the vascular tissues. This project aims to understand how the deposition of root barriers is coordinated with the arbuscular mycorrhizal and rhizobial symbioses, and how this impacts plant nutrition. The genetic model legume Medicago truncatula will be used as a discovery system since extensive genetic and biological tools for the study of both symbioses are available. By developing imaging techniques, we will describe how the root barrier deposition is coordinated with the formation of symbiotic structures. Then, we will use symbiotic mutants and single-cell transcriptomic analysis to reveal how the symbiotic pathway controls endodermal differentiation. Finally, we will investigate how impairments in root barrier deposition impact the formation of symbiotic structures and plant nutrition. Altogether, this should lead to the identification of regulatory mechanisms controlling the efficiency of symbioses, first step for the rational manipulation of plant-microbe interaction to enhance plant productivity.